The invention relates to a swivel arm assembly for a friction gear of an accessory unit in an internal combustion engine that is equipped with belt-driven auxiliary units, whereby, between a belt of the belt drive for the auxiliary units and a drive wheel of a separately provided accessory unit, a friction wheel establishing a drive connection is guided by a swivel arm that is linked so as to be pivotable about an axis on the engine side.
Such a swivel arm assembly is known, for example, from the unpublished German patent application 102 55 074, wherein an eccentric cam that is rotatably mounted in a bearing eye of the swivel arm and impinged on by a pretensioned torsion spring acts as an actuator for the swivel arm by pulling or pushing on the swivel arm in such a way that the friction wheel is held in a permanent drive connection with the belt and the drive wheel.
A refinement of this swivel arm assembly is disclosed in the likewise unpublished German patent application 103 09 063, wherein a servomotor acts on the eccentric cam in a predetermined rotational direction, via a gear with connection of a free-wheel device, for achieving a controlled interruption of the drive connection, in particular between the friction wheel and the drive wheel of the accessory unit, which preferably is designed as a coolant pump. This controlled deactivation of the coolant pump, in particular during and temporarily after a cold start of the internal combustion engine, advantageously warms up the engine more rapidly.
In the subject matter of both the cited patent applications, the respective swivel arm is situated on average essentially in the same plane as the belt driving the friction wheel, it being known that this plane of the belt is a considerable distance from the end face of the internal combustion engine. In both the referenced examples, in a corresponding adaptation to this distance an extension is situated on the end face for providing a rotational axis for the eccentric cam.
An object of the invention is to provide a swivel arm assembly by which use is made of the installation space gained by omission of the extension to obtain a compact linkage and attachment of the swivel arm in a simple mounting.
This object is achieved by a swivel arm equipped with the friction wheel forming a mounting unit having an actuator, situated on the linkage side, in an attachment device for mounting the swivel arm assembly as a whole on the internal combustion engine.
The invention is advantageous in that the swivel arm may be mounted on the internal combustion engine as a complete, structurally functional unit, and a torsion spring-loaded eccentric cam may serve as a very simple actuator and that, in a more complex embodiment of the actuator, a servomotor is associated with the eccentric cam for the controlled interruption of one of the drive connections of the friction wheel with the belt or with the drive wheel of the accessory unit.
In embodying the invention in both the simple and the complex designs of the actuator, the attachment device is a housing divided transverse to the axis on the engine side, and in one housing part a pivot is provided on which an eccentric cam serving as an actuator is rotatably mounted in a bearing eye on the linkage side, and corresponding to a torsion spring drive the eccentric cam acts on the swivel arm in the pulling direction or pushing direction to produce a permanent drive connection of the friction wheel with the belt and the drive wheel of the accessory unit.
For the controlled interruption of the friction wheel drive connection by means of a servomotor which adjusts the torsion spring-loaded eccentric cam in the opposite rotational direction in a controlled manner, in the other housing part a servomotor having a driving effect on the actuator is provided which, via a gear with connection of a blocking free-wheel device, acts in a controlled manner on the eccentric cam in a rotational direction which deactivates the friction wheel, and that in the other counterdirection of the eccentric cam which activates the friction wheel a pretensioned torsion spring drives the eccentric cam, whereby the unblocked free-wheel device causes a rotational interruption with respect to the servomotor.
According to the invention, the placement of the swivel arm linkage and the actuator in a multipart housing used as an attachment device achieves an advantageously compact design of the swivel arm assembly for simple mounting of same to the internal combustion engine.
In a further embodiment of the invention, a conventional direct-current motor, brushless direct-current motor, or electric stepping motor is preferably used as the actuator drive for a servomotor, and a multistage-reducing spur gear or a planetary gear is provided as the gear.
The attachment device designed as a housing according to the invention has an advantageously simple structure by the fact that the housing, having mutually centered housing parts, is attached to the internal combustion engine via corresponding flanges with openings placed on the housing parts and by use of screw bolts which extend through the housing parts, and damping elements coaxial with the screw bolts are optionally provided in the openings in both flanges to achieve a damping effect. In this manner, transmission of structure-borne noise is advantageously counteracted.
With regard to the swivel arm linkage in the housing, the housing has a passage on the outer periphery which is covered by an elastic bellows that encloses the swivel arm on the bearing eye side.
Lastly, a smooth-walled design of the swivel arm assembly advantageous for handling during mounting is achieved by the fact that the swivel arm is formed from elements having a half-shell shape, situated on both sides of a longitudinal plane in the region of the arm section of the swivel arm and in the region of a one-piece, flat-cylindrical protective housing integrally molded thereon for the friction wheel, and the elements, which are detachably or nondetachably connected to one another and enclose a hollow profile in the arm section, in each case are in one-piece connection with an axial portion of the swivel arm bearing eye. The design described above also results in a flexurally and torsionally rigid swivel arm.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings for example.